The present invention relates to a traction controller for a vehicle.
In general, there has been known traction control in which engine outputs and/or the application of braking force to a wheel are controlled (the engine outputs are lowered or the braking force is increased) such that the spin value of a driving wheel to be detected can become a target one in order to prevent the driving wheel from extreme spinning by an excessive driving torque, so as to enhance an acceleratability.
There has been known the proposal in which a G sensor for detecting the lateral acceleration of the vehicle is provided in an antiskid brake controller so as to correct the braking target value of the speed or deceleration of right and left wheels according to the lateral acceleration (see Japanese Examined Patent Publication Gazette No. 63-66703).
In the case where the vehicle is to be turned, the driving wheels can easily spin. Under the circumstances, the lateral acceleration is generated on the vehicle. In the vehicle having a traction controller, it is desired that when the lateral acceleration is greater, traction (spin) control is started earlier or a control quantity is increased. Consequently, it is possible to prevent a great spin from being caused.
However, it is necessary to provide the G sensor in order to detect the lateral acceleration.
In general, there has been known that the lateral acceleration can be calculated based on a vehicle speed and a vehicle turning radius. Accordingly, it is supposed that the lateral acceleration is obtained by calculation instead of using the G sensor. However, if the lateral acceleration is detected based on the actual turning radius of the vehicle so as to correct the traction control, there cannot necessarily be carried out the traction control suitable for the state of the vehicle.
By way of example, when the vehicle speed is high, a handle steering angle is great or a road friction coefficient is low at the time of turning, the actual turning line of the vehicle can easily deviate from a line intended by a driver, i.e., an under-steering (hereinafter referred to as under-steer) tendency becomes marked. In this case, it is sufficient that the traction control is started earlier or the control quantity is increased. However, when there is an under-steer tendency, the actual turning radius of the vehicle is increased so that the lateral acceleration obtained by the calculation is made smaller. Consequently, it is impossible to necessarily start the traction control early and increase the control quantity by request.